This disclosure pertains to optical sensor systems in general and in particular to a multi-function airborne sensor system combining infrared search and track (IRST), targeting, and standoff reconnaissance functions in the same airborne sensor system.
Demand for imaging sensors that provide infrared search and track (IRST), targeting or standoff reconnaissance functions is increasing. These type of sensors can be used in various applications such as on an aircraft including an unmanned aerial vehicle (UAV) platform for standoff reconnaissance or on a jet aircraft for IRST, targeting and standoff reconnaissance.
IRST is often used for detecting and tracking objects which emit infrared radiation such as jet aircrafts, helicopters, etc. Generally, IRST systems are passive in that they do not transmit or send any radiation of their own unlike radar or Light Detection and Ranging (LIDAR) or Laser Detection and Ranging (LADAR). However, some IRST systems can incorporate laser rangefinders to provide information on an object's position. IRST system are currently used in many aircrafts, particularly, fighter aircrafts to provide air superiority. As its name indicates, an IRST system operates generally in the infrared wavelength range, but visible wavelength sensing capability is typically also desired within the IRST sensor.
Stand-off reconnaissance also known as “scouting” is used for survey or observation to gain or collect image information which can be used for intelligence gathering. The wavelength ranges of interest for standoff reconnaissance include the visible wavelength range between about 0.4 μm and about 0.7 μm, near-infrared wavelength range between about 0.7 μm and about 1 μm, the short wavelength infrared radiation (SWIR) in the wavelength range between approximately 1 μm and 3 μm, mid wavelength infrared radiation (MWIR) in the wavelength range between approximately 3 μm and 5 μm, and long wavelength infrared radiation (LWIR) in the wavelength range between approximately 8 μm and 12 μm.
Targeting, on the other hand, is used for target location and designation, for example, in fighter aircrafts and bombers for identifying targets and guiding precision guided munitions such as laser-guided bombs or missiles to designated targets. Some targeting systems have a laser (e.g., an infrared laser) that can designate a target for laser-guided munitions, enabling an aircraft carrying a targeting system to designate its own targets or designate targets for other friendly units. An additional active laser function that may also be implemented in a targeting sensor is laser rangefinding.
Currently, each of the IRST function, standoff reconnaissance function and targeting function is provided as a separate sensor system. Therefore, a user desiring to utilize two or more of these functions is required to purchase two or more separate sensor systems which can increase the overall cost of owning such separate sensor systems. In addition to the cost, providing two or more of such separate sensor system on a user platform increases the overall complexity. This separation of the three sensing functions into three separate sensor systems has generally been motivated by, among other things, the significantly different fields of regard required for each sensing function: a) the IRST field of regard is very wide in azimuth (horizontal), but generally forward looking, b) the standoff reconnaissance field of regard is wide in pitch (horizontal), but generally side looking, and c) the targeting field of regard is very wide in elevation, and can extend from many degrees above the local horizon (forward) to many degrees past (behind) the local nadir (vertical) by as much as 60 deg.
In addition, none of these three separate sensor systems currently has the capability to incorporate advanced coherent LADAR subsystems such as long range vibrometry. Prior attempts to add advanced LADAR capability to any of the IRST sensor system, standoff reconnaissance sensor system and targeting system has met with limited success due to the fact that adding such advanced LADAR capability compromises some of the original sensor (IRST, targeting, or standoff reconnaissance) capabilities. Furthermore, the stability requirements that are needed for such an advanced LADAR function are not characteristic of existing sensor approaches for IRST, targeting, or stand-off reconnaissance functions.
Hence, there is a need in the art for a multi-function airborne sensor system that is able to combine infrared search and track (IRST), targeting and standoff reconnaissance functions on the same airborne system. There is also a need for a system that further provides advanced coherent LADAR function.